I try to use NUMAKER-PFM-M487 + ESP8266 to run mbed client application, but sometimes the application works well, sometimes it works fail. I find in fail cases, the root cause is the CIPSEND AT command can only receive "Recv xx bytes" message, but never wait for "SEND OK" message.

In below log, the "AT? XXX" means the program is waiting for XXX, and "AT= XXX" means the program already get XXX message. You can see the first 643 bytes is send ok, but the second 75 bytes is send fail. In mbed, the default timeout of ESP8266 is 2 second. After increase the timeout to 5 second and 10 second, the program still cannot wait for "SEND OK" message from ESP8266.

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